[llvm-dev] Missing kill flag on Machine Instruction operands

[Stephen Rogers via llvm-dev]

Hi Quentin,

That's unfortunate to hear. I'll take a look into using the LiveInterval
analysis for this.

Thanks for the advice,
Stephen

On 9 May 2016 at 17:05, Quentin Colombet <qcolombet at apple.com> wrote:

> Hi Stephen,
>
> The kill flags are conservatively correct and not mandatory; if they are
> set, they are correct, if they are not, you cannot say anything.
>
> On May 9, 2016, at 8:37 AM, Stephen Rogers via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi all,
>
> I'm writing a MachineFunction pass that relies on the kill flag to be
> appropriately set on operands of Machine Instructions, but it isn't. My
> pass runs before register allocation. What I'm seeing when I print an
> instruction is something like:
>
> %vreg218<def> = FOO %vreg217, %vreg369
>
> but what I need is:
>
> %vreg218<def> = FOO %vreg217<kill>, %vreg369<kill>
>
> On this same instruction, the kill flag is being set on vreg217 and
> vreg369 in preceding and succeeding passes, but not in my pass. Is there
> some analysis pass that I need to add as required in my pass's
> "getAnalysisUsage" to get this flag to be set?
>
>
> I would recommend to rely on the LiveInterval analysis.
>
> Cheers,
> -Quentin
>
>
> Thanks,
> Stephen
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